The San Juan Islands lie in the Salish Sea, and diving here takes in a varied mix of reef, wall, kelp forest, wreck, and drop-off topography. Sites range from shallow accessible entries to walls descending to sixty metres. Water stays cool year-round, warming slightly in late summer but never warm enough to dive comfortably without a drysuit or thick wetsuit. Nudibranchs are prolific, with multiple species recorded including branched dendronotids and three-lined aeolids, alongside harbour seals, Steller sea lions, Dungeness crab, kelp greenling, and Pacific electric rays. Currents are a significant planning factor at exposed sites, and divers should time entries around tidal movements.
Monthly water temperature across San Juan Islands's sites, from satellite sea-surface data corrected for depth. The band shows the site-to-site spread.
Water temperature stays relatively stable in winter and rises moderately through summer, with the warmest conditions in late summer. Currents vary considerably between sites; sheltered locations such as Lake Whatcom offer calm conditions, while Lime Kiln Point sees strong tidal flow that limits diver access to specific windows.
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Water temperature around San Juan Islands ranges from about 8°C in January to 13°C in August, based on satellite sea-temperature data for its dive sites.
In the warm season (about 13°C) a 7mm or semi-dry suit is comfortable in San Juan Islands; in the coldest months (about 8°C) step up to a drysuit.
Fin maps 8 sites in San Juan Islands (7 scuba diving sites and 2 snorkelling spots, with some suited to both).
2 more sites to explore
